Prisma · Const

@@unique

@@unique defines a compound unique constraint across specified model fields. Every participating field must be mandatory, and Prisma adds a corresponding unique index.

How it works

Place @@unique on a model to require that the combination of listed fields is unique. Prisma creates the corresponding unique index, and the fields must be mandatory; optional fields cannot participate in the constraint.

Syntax

@@unique(_ fields: FieldReference[], name: String?, map: String?, where: raw(String) | { field: value }?)

Parameters

Name	Type	Description
`fields`	`FieldReference[]`	Fields making up the compound constraint; every field must be mandatory.
`name`	`String?`	Optional Prisma-level name for the constraint.
`map`	`String?`	Optional database-level mapped name.
`where`	`raw(String) \| { field: value }?`	Optional raw filter expression or field-value object.

Returns

A model-level compound unique constraint and corresponding unique index.

Key points

It enforces uniqueness on a combination of fields at the model level.
Several different field combinations can each have their own compound constraint.
The declaration also results in a unique index for the selected database columns.
The fields list can include a length modifier for supported fields.
Field entries can specify descending or ascending sort order.

Common mistakes

Do not include optional fields in the compound constraint.
A model without an ID needs this block when it is the model's sole unique identifier.

Example: Compound uniqueness for a model

model Post {
  id       Int    @id @default(autoincrement())
  authorId Int
  title    String

  @@unique([authorId, title])
}

Ensures an author cannot have two posts with the same title.

When to use it

Scoped uniqueness

Prevent duplicate titles within the same author or owner.

Compound business identifier

Represent a natural key made from multiple required columns.

Database naming

Control generated constraint and index names.

Interview questions

QWhat does @@unique do?

@@unique defines a compound unique constraint across multiple model fields. Prisma also adds a corresponding unique index for those columns.

Follow-up: What restriction applies to the participating fields? They must all be mandatory, not optional.

QHow do you declare a compound unique constraint?

Use the fields argument with a list such as @@unique([authorId, title]). The combination, rather than either field independently, must be unique.

Follow-up: How would you make the database object name explicit? Supply the name or map argument in the attribute.

QHow many @@unique blocks can a model have, and when is one required?

A model can contain multiple @@unique blocks. If it has no @id or @@id, a @@unique block is required when it is the model's only unique constraint.

Follow-up: Can @@unique replace every identifier requirement? No; the model still needs at least one unique identifier, and the documented rule applies when it is the sole one.

@unique
@@id
@id
unique index
compound unique constraint

Source: Prisma Schema API (Prisma ORM v7). Checked 2026-10-16.